Vibrating sensors, such as for example, vibrating densitometers and Coriolis flowmeters are generally known, and are used to measure mass flow and other information related to materials flowing through a conduit in the flowmeter. Exemplary Coriolis flowmeters are disclosed in U.S. Pat. No. 4,109,524, U.S. Pat. No. 4,491,025, and Re. 31,450, all to J. E. Smith et al. These flowmeters have one or more conduits of a straight or curved configuration. Each conduit configuration in a Coriolis mass flowmeter, for example, has a set of natural vibration modes, which may be of simple bending, torsional, or coupled type. Each conduit can be driven to oscillate at a preferred mode.
Some types of mass flowmeters, especially Coriolis flowmeters, are capable of being operated in a manner that performs a direct measurement of density to provide volumetric information through the quotient of mass over density. See, e.g., U.S. Pat. No. 4,872,351 to Ruesch for a net oil computer that uses a Coriolis flowmeter to measure the density of an unknown multiphase fluid. U.S. Pat. No. 5,687,100 to Buttler et al. teaches a Coriolis effect densitometer that corrects the density readings for mass flow rate effects in a mass flowmeter operating as a vibrating tube densitometer.
Material flows into the flowmeter from a connected pipeline on the inlet side of the flowmeter, is directed through the conduit(s), and exits the flowmeter through the outlet side of the flowmeter. The natural vibration modes of the vibrating system are defined in part by the combined mass of the conduits and the material flowing within the conduits.
When there is no flow through the flowmeter, a driving force applied to the conduit(s) causes all points along the conduit(s) to oscillate with identical phase or with a small “zero offset”, which is a time delay measured at zero flow. As material begins to flow through the flowmeter, Coriolis forces cause each point along the conduit(s) to have a different phase. For example, the phase at the inlet end of the flowmeter lags the phase at the centralized driver position, while the phase at the outlet leads the phase at the centralized driver position. Pickoffs on the conduit(s) produce sinusoidal signals representative of the motion of the conduit(s). Signals output from the pickoffs are processed to determine the time delay between the pickoffs. The time delay between the two or more pickoffs is proportional to the mass flow rate of material flowing through the conduit(s).
Meter electronics connected to the driver generate a drive signal to operate the driver and also to determine a mass flow rate and/or other properties of a process material from signals received from the pickoffs. The driver may comprise one of many well known arrangements; however, a magnet and an opposing drive coil have received great success in the flowmeter industry. An alternating current is passed to the drive coil for vibrating the conduit(s) at a desired flow tube amplitude and frequency. It is also known in the art to provide the pickoffs as a magnet and coil arrangement very similar to the driver arrangement. However, while the driver receives a current which induces a motion, the pickoffs can use the motion provided by the driver to induce a voltage. The magnitude of the time delay measured by the pickoffs is very small; often measured in nanoseconds. Therefore, it is necessary to have the transducer output be very accurate.
Generally, a flowmeter can be initially calibrated and a flow calibration factor along with a zero offset can be generated. In use, the flow calibration factor can be multiplied by the time delay measured by the pickoffs minus the zero offset to generate a mass flow rate. In most situations, the flowmeter is initially calibrated, typically by the manufacturer, and assumed to provide accurate measurements without subsequent calibrations required. In addition, a prior art approach involves a user zero-calibrating the flowmeter after installation by stopping flow, closing valves, and therefore providing the meter a zero flow rate reference at process conditions.
Vibrating sensors, including Coriolis flowmeters, are often employed in large engine systems, such as those found in marine vessels. For such vessels, proper fuel management is critical for efficient engine system operation. Fuel management typically begins with the bunkering, or fuel loading, at port. It is at this point where fuel is loaded onto the vessel and the quantity is measured. Fuel quality, however, is not known at this time. Fuel quality is determined by sending samples to a laboratory where viscosity, density, and composition may be determined. Unfortunately, this process often takes several days, so fuel quality issues that arise are typically only uncovered after the vessel has left port and is well underway at sea. Additionally, even if fuel quality meets a given set of standards, problems within a fuel system can introduce contaminants, such as water, into the fuel system, which is problematic.
Therefore, there is a need in the art for a method and related apparatus to determine qualitative fuel attributes. There is a need for a method and related apparatus to determine fuel density before entering and after exiting an engine. There is a need to detect potential water content of the fuel. The present invention overcomes these and other problems and an advance in the art is achieved.